//
// Created by ashCheng on 2022/12/2.
//
#include <iostream>
#include "Sales_item.h"

int main() {
  Sales_item item1, item2;
  std::cin >> item1 >> item2;
  if (item1.isbn() == item2.isbn()) {
    std::cout << "Sum: " << item1 + item2 << std::endl;
    return 0;
  } else {
    std::cout << "Different isbn." << std::endl;
    return -1;
  }
}